It’s always good to be nice to people who hold power in the service industry. The restaurant hostess can give you a table next to the window or the washrooms. A hotel front desk clerk can assign you a room overlooking the lake or a lackluster parking lot. Similarly, the agent at the rental car counter has the power to stick you in the crappiest, oldest car in the farthest end of the lot or send you on your way in a nice set of wheels.

A former rental car agent shares his tips on how to land a better rental car by avoiding these seven deadly sins.

7 Deadly Sins Keeping You From Getting a Better Rental Car

1. You don’t have your driver’s license and credit card ready.

The very first thing the computer will prompt the agent to request is your address and driver’s license information, followed by your credit card info. Nothing can happen until the agent has both items, and asking why they are required and then wasting time digging around in your bag looking for them is a sure way to annoy the counter agent and everyone in line behind you.

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Instead, be prepared. Arrive at the counter with your driver’s license and credit card already out. Or better yet, sign up for the company’s frequent renter loyalty program, which will store all your information so the agent will already have access to it.

2. You say upfront that you don’t want insurance.

Rental agents make their living on commissions. At least let an agent try to sell you something, since a goose egg hurts his performance numbers and take-home pay. Now, don’t get us wrong—we recommend that you decline every extra item that you don’t need. But at least understand how it works.

Instead, even if you’re dead-set against add-ons, wait for the agent to ask, and then just politely say, “No, thanks, I appreciate the offer, but I’m good.” He may try again, but he’ll respect your decision and not be annoyed.

3. You ask for a “free upgrade.”

Asking for free stuff will encourage the agent to make sure you get exactly what you booked. Why? First, she may be annoyed at your cheekiness to outright ask for something for free. Would you ask your waitress to upgrade to the larger beverage for free?

Second, you’ve tipped your hand. Now the agent knows you’re interested in something bigger, which gives her an upper hand in negotiating with you. Understand that she can earn a commission by getting another customer to pay for an upgrade, so she’s not going to give it away for free just because you asked.

Instead, use legitimate ways to improve your chances of scoring an upgrade. The most surefire is to show up when the agent has sold out of your car class. That means she will automatically give you the next size up that is available—though she may not admit that to you.

You can also try negotiating. Suggest that you’ll buy an add-on that you actually need, such as liability coverage, if she is able to upgrade you to a nicer car. That turns the situation into a win-win for both of you.

Finally, the best strategy of all may be to simply be nice. Let the agent knows that you’d really enjoy a nicer car but let her think you’re on a tight budget. Ask how much extra it would cost to upgrade. She might be happy to let you into something nice for $5 or $10 a day extra.

4. You are super picky about the make and model of your car.

If all that is available in your reserved class is a Hyundai Sonata, don’t pitch a fit and demand an American car. We’re all for supporting local, and the agent knows that a Toyota may be more likely made in America than some American makes that are assembled in Canada or Mexico. But he won’t want to argue with you about it.

Also, rental companies aim to provide functional transportation, not cater to high-maintenance people. If you’re nice and the agent has a selection available, he may be willing to let you pick, but if you’re very pushy, he’ll be sure to make sure you get exactly what you don’t want. Remember, he has the power here.

Instead, be creative, like the guy who got assigned a Suzuki SUV and then confessed that he’d be shot if he showed up at his union convention in a foreign car. The agent laughed and found him a Jeep. Be human and make the agent a friend and he’ll take care of you.

5. You joke about violating the rental agreement.

Most agents actually like their jobs and care about protecting the company’s assets. If you’re going to hint that you won’t take care of the car, you just may land the junkiest car on the lot—or no car at all.

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6. You bring up the Seinfeld rental car clip.

It was funny the first 99 times we all saw it. Agents might even still chuckle at the truth in the clip but know that you’ll be the 10,000th customer to mention it.

7. You get mad at the agent for the taxes and fees.

Your agent would probably agree that the Vehicle Licensing Fee and Energy Recovery Fee are part of the cost of doing business and should be built into the rate. But she has zero control over that 10% fee going to the county or the 11.1% going to the airport authority. Yelling at her isn’t going to make those costs go away. She has no power to change this situation.

The truth is that most rental car agents enjoy their jobs and their customers. Just always remember that there is a human behind the counter and that you always catch more flies with honey than with vinegar.